1. Field of the Invention
The present invention relates to a pumping brake detection and control device and method for detecting a pumping brake operation, and more particularly, to a pumping brake detection and control device and method for an internal combustion engine.
2. Description of the Related Art
A vehicle is generally provided with a brake booster for assisting an operation force applied by a driver to depress a brake pedal. An intake pipe for introducing the air is provided for an internal combustion engine, and a negative pressure (as used herein, pressure lower than the atmospheric pressure) is generated in the intake pipe when the air is introduced into a combustion chamber of the internal combustion engine therethrough. The brake booster uses the negative pressure generated in the intake pipe as a power source. The negative pressure is led to the brake booster via a brake pressure feeding pipe which branches from the intake pipe at the downstream side of the throttle valve. An adjusting valve which is operated by the air pressure in the brake booster is provided. When the driver depresses the brake pedal, the adjusting valve is operated by the negative pressure corresponding to a depression quantity of the brake pedal to assist the depressing operation force applied to the brake.
The negative pressure is secured by closing the throttle valve in order to drive the brake booster. However, when a pumping brake operation in which the driver repeats an operation of stepping on the brake is performed, the air is introduced from the brake booster to the intake pipe, the pressure inside the intake pipe changes to the atmospheric pressure, and it is hard to secure the negative pressure required for driving the brake booster. Therefore, the brake booster no longer assists the depressing operation force on the brake, and the driver feels discomfort. Note that, the pumping brake operation is one of driving techniques of the driver, and at the time of driving on a frozen road surface or a snowy road, repeats an action in which the brake pedal is gradually depressed without fully depressing the brake pedal at once, and the brake pedal is slightly released when wheels start slipping, and the brake pedal is stepped on again. By performing the pumping brake operation, the braking distance during the braking can be minimized by preventing the wheels from being locked.
As a method for detecting the pumping brake operation, for example, in a negative pressure control device for a vehicular internal combustion engine according to Japanese Patent Application Laid-open No. 2000-110606, whether the pumping brake operation is being carried out or not is detected based on a period from a braking operation to a next braking operation.
An on/off state of a brake switch is determined based on the depression quantity of the brake pedal according to Japanese Patent Application Laid-open No. 2000-110606. In other words, if the depression quantity of the brake pedal is “0”, it is determined that the brake switch is off, and if the depression quantity of the brake pedal is other than “0”, it is determined that the brake switch is on. However, the brake switch generally chatters. For example, the brake switch chatters due to a vibration of a brake pedal when the brake pedal is released in the brake operation. As a result, whether the brake switch is on or off is erroneously determined, and as a result, it is erroneously determined that the driver is carrying out the pumping brake operation. Therefore, a control generally provides hysteresis for the determination regarding the brake switch.
However, if the hysteresis is provided, even when the brake switch is turned off from on (or conversely on from off), the turning on/off of the brake switch is neglected due to the hysteresis, and the pumping brake operation may not be detected. As a result, the air is introduced from the brake booster to the intake pipe, the pressure inside the intake pipe changes to the atmospheric pressure, and it is thus difficult to maintain the negative pressure required to drive the brake booster.